This invention relates to improved cylinder porting which is especially useful in multi-piston assemblies, and to an add-on cylinder and piston assembly.
Multi piston assemblies have been utilized, as for example, in fluid actuated hand tools such as shown in U.S. Pat. No. 3,323,346. Such devices have been limited in their operation due to the necessity for porting the multi-piston arrangement by utilizing a port in an end cap together with axial porting in a series of piston rods. In addition, in order to retract the multi-piston arrangement, it has been necessary to utilize either a spring or outside tubing for supplying fluid under pressure to a remote piston. Since such multi-piston devices must be ported through the piston rod, it has been necessary that the piston rod be inordinately large to accommodate the longitudinal porting passageways. Thus, the piston area for engagement by the pressurized fluid is limited by the size of the piston rod so that the total force exerted by the assembly is likewise limited. Moreover, porting through the piston rods necessitates an expensive manufacturing process requiring complicated molds or machining operations. The position of a fluid supply bore in one of the end caps limits the mode of actuation of the fluid operated assembly.
Because such inlet ports in end caps are operated by transverse valve operators, the use of elongated pivoted handles extending at right angles thereto and in alignment with the cylinders have been necessitated. Such hand held multi-piston assemblies are often used to power crimping tools carried by the cylinders remote from the inlets and because such tools are operated with great force by the multi-piston arrangements, inadvertent actuation thereof may be hazardous to the operator and others nearby. This hazard is increased by the necessity for utilizing a pivoted handle exposed along the outside of the cylinder. Firing of the multi-piston arrangement through actuation of the pivoted handle may occur inadvertently or as a result of dropping of the tool by an operator.
Since porting arrangements utilized heretofore require the valve and end port to be carried at the end cap opposite the power operated tool, it has never been known or thought to be desirable to provide an axial add-on component to increase the number of serially arranged pistons where it is desirable to increase the force which may be applied by such an assembly. While the apparatus illustrated herein is particularly related to using of the apparatus and method with a multi-piston fluid operated tool, it is to be understood that such assemblies and method are useful for any other applications where extraordinary force is required to be generated in a fluid operated apparatus.
Moreover, porting as has been provided utilizing bores in the cylinder side walls has required external right angled drilling in order to communicate with the inside of the cylinder. This requires the use of plugs to block off the longitudinal ports from the outside of the cylinder. Such plugging is expensive and often unsatisfactory due to leakage.